From 53461deb04ecddf3be8b8b03024bb8bbc08b9d6b Mon Sep 17 00:00:00 2001
From: Tom Collins <tom.collins@digi.com>
Date: Fri, 12 May 2017 13:30:12 -0700
Subject: py/objstringio: Fix StringIO reads at or beyond EOF.

Existing code failed if seek() went past EOF (which is acceptable when writing).
---
 py/objstringio.c | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'py')

diff --git a/py/objstringio.c b/py/objstringio.c
index 88659deb89..f4e7967807 100644
--- a/py/objstringio.c
+++ b/py/objstringio.c
@@ -56,6 +56,9 @@ STATIC mp_uint_t stringio_read(mp_obj_t o_in, void *buf, mp_uint_t size, int *er
     (void)errcode;
     mp_obj_stringio_t *o = MP_OBJ_TO_PTR(o_in);
     check_stringio_is_open(o);
+    if (o->vstr->len <= o->pos) {  // read to EOF, or seeked to EOF or beyond
+        return 0;
+    }
     mp_uint_t remaining = o->vstr->len - o->pos;
     if (size > remaining) {
         size = remaining;
-- 
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